The present invention relates to mixture control systems for an internal combustion engine, and in particular to a closed-loop mixture control system using an exhaust composition sensor and a catalytic converter wherein the system can adapt to varying engine operating conditions.
Closed-loop mixture control systems using an exhaust composition sensor and a catalytic converter are known in the art. However, due to the inherent time delay in the feedback control loop, the introduction of a sudden change to the operating conditions of an internal combustion engine will result in the generation of an inappropriate control signal during transitional periods and thus the system cannot adapt precisely to varying engine operating conditions. Such abrupt changes are often triggered by sudden shifting of throttle positions as the vehicle is accelerated or decelerated.